[TowerTalk] Rohn 25 Tiltover ideas?

[jimlux]

Kevin Normoyle wrote:
> The wind turbine guys do tiltups a lot. (usually just poles though)
> I did a quick look and found some interesting pics from five 60 meter 
> tall 25g tiltups being used for wind speed instruments (with 8" screw 
> anchors). 4 guys. (a lot of them).
> 
> http://www.hi-techtowers.com/imageview.aspx?pic=37_pic3.jpg
> http://www.hi-techtowers.com/imageview.aspx?pic=37_pic1.jpg
> http://www.hi-techtowers.com/imageview.aspx?pic=37_pic2.jpg
> http://www.hi-techtowers.com/imageview.aspx?pic=37_pic5.jpg
> 
> Gotta love the bales of hay in the next to last picture. Use what you got!


I think that plethora of guys is how you make it work with a long skinny 
mast.  If properly done, they distribute the load so the bending forces 
aren't huge. If these guys are doing a sort of standard installation a a 
bunch of times, then they can
a) have an engineer do all the calculations to figure out the best 
length for the guys, the derrick, etc, and determine the bending forces 
at each step of the process.
b) do some testing
c) Develop a standard procedure which is bulletproof.

This is, of course, different than the notional ham scenario where you 
have someone who is erecting only a few towers in their lifetime, 
scrounging bits and pieces from a variety of sources, etc.

I'll note that the calculation of forces with multiple guys hanging from 
the derrick and along the mast is going to require some sort of FEM 
program, is  as opposed to some sort of handy Excel spreadsheet. 
Especially if you want to consider windloads during erection.  Simple 
FEM, but definitely not in the cookbook category.